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More information about Masjed Soleiman drilling project;

Masjed Soleiman Hydroelectric

Power Plant

Client:  Ab-Niroo

Engineer:  Moshanir

Contractor:  Hara Institue

Masjed Soleiman is an important underground hydroelectric power plant in Iran.  It is built on Karun river and the dam body is a rock fill type which was finished in year 2000.  The dam has been designed to provide enough water to run the underground power plant with 2000MW capacity annually.  The power house is built at two stages.  Phase one which was completed almost in 2002, is in operation and the second phase is under construction.  The excavation stages of the second phase (known as extension phase) was started by Hara Institute in 1998 and it is almost ended (in 2003). the concrete work is going to be started in 2003 and ending in 2004.  The rock mass at this site includes compacted conglomerates, sandstones and claystones.  They are generally inclined at about 20 degrees from horizontal from down stream towards the upstream.  The claystone layer daylights at the roof elevation and also at the mid-hight of the cavern wall in downstream side.  The strike of the layers are almost the same as the axis of the caverns so one can see the claystone-conglomerate contact almost all along the cavern length.

Due to the high amount of stresses in the roof along with the large size of the cavern, some deformations (in excess of the designed limits) were observed in this contact.  In phase I, this could cause some local instabilities which was later reinforced by putting long groun anchors.  The engineer of the site decided to put the same type of reinforcing system in the roof in the extension phase to prohibit the same instabilities at earlier sages.  The design was to put 450 ground anchors, the length of which was in the range of 15-20 meters.  They were supposed to be permanent therefore they should have been Double Corrosion Protected (DCP) anchors. 

The drilling was done by DTH hammers from platforms about 20 meters above the floor level in the cavern.  The plat forms rested on the crane concrete beams which was earlier attached to the walls of the caverns with long cable tendons.  The problems associated with the difficult access and supply of the materials are amongst the wide range of problems in this project.  The hole diameter was 110 mm and tendons were put in them, grouted in place and stressed to the required level after hardening.  The  job was performed at 6 months with 2 shifts 11 hours each.  After completion of this job, further excavation of the cavern was permitted by the engineer to ensure a safe and reliable construction.

The ground anchors were supplied by SAH company, from Germany and all of the required work to drill, assemble, installation and stressing of them were done by Payab Zamzam Engineering Services.

The work was performed from  the top of a 25 ton crane in the 232 level at the main cavern and the axcess to the roof was facilitated by manufacturing a platform on top of the crane.  At the time of erection of the platforms, the floor of the cavern was 20 meters bellow the level of the crane.

At first, all of the pieces of the tendon system was gathered together at an assemblage site.  These included both big pieces of plstic and steel bars as well as small pieces of plastic.

The first stage of assembly is to wash the monobars and to remove the surface staining and grease to assure perfect bond between the bar and cement.

The next stage is to attach the internal spacers to the monobars so that the internal grout makes a uniform cylinder around the bar.

Measuring the required length of the corrugated pipe was the next task.

The pipe is then run through the monobars and the internal spacers.

When all these are done, the grout valve is attached to the bar and the system gets ready to be grouted.

The assembled monobars then rest on a slope which is carefully fixed and designed in term of the slope to make sure the smooth de-aired filling of the whole system.  After grouting is completed and the cement is hardened, the grout valve is removed and the tendon ends are brushed clean to get ready for shipment to the installation site.

Before moving the system, the external spacers are fixed which ensures the tendon to rest centre in the borehole.  In this configuration, the grout will penetrate all around the tendon in the hole.

The tendon is transfered with extra care to make sure no sag is imposed to the tendon.

When the tendons go to the place, the boreholes which are drilled by a DTH drilling system are cleaned and the tendon gets ready to be pushed into the holes.

Pushing the tendon into the boreholes are done by hydraulic pushing system.

When the tendon is grouted and hardened in the hole, the stressing equipments are installed on the collar and applies the designated loading sequences.  This can be either Simple Stressing Test (SST) sequence or more completely by Comprehensive Stressing Test (CST) sequence as ordered by the engineer.

All above tasks for 445 tendons were performed by Payab Zamzam Company during 150 working days and the site was handed over to the client for further excavations.

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